Drum printer

ABSTRACT

A high speed printer has a drum with a cylindrical wall of resilient material. On the cylindrical wall, a series of type formations are arranged in a helical path about the external periphery. A feeding mechanism is provided for operating a printing medium past the periphery of the drum, in contiguity with the type formations. Driving means is provided for rotating the drum about the axis of the helical path and at the same time translating the drum longitudinally along the axis so that each type formation passes in substantially continuous succession past each of a plurality of spaced printing positions on the medium. A hammer element is located substantially inside of the drum. This hammer element is movable by the driving means together with the drum when the latter is translated longitudinally along its axis. When the hammer element is selectively actuated against the inside of the cylindrical wall of the drum behind a selected type element, resilient flexing of the cylindrical wall selectively imprints characters on the medium.

United States Patent 1191 Bowdle et al.

[4 Oct. 21, 1975 DRUM PRINTER [75] Inventors: Raymond Ralph Bowdle,Morgan Hill; Robert Junior Laybourn, San Jose, both of Calif.

[73] Assignee: International Business Machines Corporation, Armonk, NY.

[22] Filed: Aug. 28, 1972 [21] Appl. No.: 284,297

[44] Published under the Trial Voluntary Protest Program on January 28,1975 as document no. B 284,297.

[52] US. Cl. 197/54; 101/93.16; 101/93.23;

101/109 [51] Int. Cl. B41J l/34 [58] Field of Search 101/93,111, 109,110; 197/53, 55, 18, 49, 1 R, 54

[56] References Cited UNITED STATES PATENTS 2,843,243 7/1958 Masterson197/19 2,958,568 11/1960 Hagelbarger... 197/1 R 3,295,652 1/1967 Sasaki197/53 3,326,346 6/1967 Sasaki 101/111 X 3,378,127 4/1968 Clary et al.197/53 3,384,216 5/1968 Thayer 197/53 3,408,930 11/1968 Chamness et a1101/93 3,415,184 12/1968 Perucca 10l/93 C 3,589,494 6/1971 Gloess 197/183,651,914 3/1972 Locke 197/49 3,651,916 3/1972 Becchi 101/93 C 3,717,2342/1973 Koller 197/53 FOREIGN PATENTS OR APPLICATIONS 1,239,360 7/1971United Kingdom Primary ExaminerRobert E. Bagwill Assistant ExaminerPaulJ. Hirsch Attorney, Agent, or Firm-Shelley M. Beckstrand [57] ABSTRACT Ahigh speed printer has a drum with a cylindrical wall of resilientmaterial. On the cylindrical wall, a series of type formations arearranged in a helical path about the external periphery. A feedingmechanism is provided for operating a printing medium past the peripheryof the drum, in contiguity with the type forma tions. Driving means isprovided for rotating the drum about the axis of the helical path and atthe same time translating the drum longitudinally along the axis so thateach type formation passes in substantially continuous succession pasteach of a plurality of spaced printing positions on the medium. A hammerelement is located substantially inside of the drum. This hammer elementis movable by the driving means together with the drum when the latteris translated longitudinally along its axis. When the hammer element isselectively actuated against the inside of the cylindrical wall of thedrum behind a selected type element, resilient flexing of thecylindrical wall selectively imprints characters on the medium.

5 Claims, 7 Drawing Figures .U.S. Patent Oct. 21, 1975 -Sheet10f23,913,722

US. Patent Oct.21, 1975 Sheet2of2 3,913,722

FIG.5

FIG.4

FIG.3

PTAPE DRUM PRINTER BACKGROUND OF THE INVENTION 1. Field of the InventionThis invention relates to a novel and improved drum printer forrecording characters on a medium.

2. Description of the Prior Art A typical type of prior art drum printeris structured so that a formation of type elements is arranged in ahelical path on the external periphery of the drum and a striking memberor hammer acts to compress the medium between a face of the hammer andthe type elements on the external drum surface. The drum is commonlydriven in such a manner that it rotates about its axis and at the sametime also translates longitudinally along the axis so that each typeelement passes each of the plurality of spaced printing positions of themedium, in substantially continuous succession.

Efforts have been made in recent years to provide a lowcost and compacttype of drum printer. For example, drum printers have been provided withradially movable types that are struck by a hammer located inside of adrum. However, these devices have been considered somewhat bulky,unreliable, and also uneconomical in assembly and material costs.Accordingly, it has been found desirable to provide a low-cost, compactand improved drum printer which overcomes the disadvantages of suchknown prior art techniques.

SUMMARY OF THE INVENTION An important object of this invention is toprovide a novel and improved drum printer structured so that it may bevery small in size, yet low in cost.

Another object of this invention is to provide an improved drum printerwhich uses a drum of resilient material.

A further object of our invention is to provide a drum printer having aresilient cylindrical wall for supporting type formations, and a hammerarranged inside of the drum for front printing.

Still another object of this invention is to provide an improved drumprinter wherein the type font is arranged on the drum in a spiralfashion and the drum is capable of continuously scanning a page withoutescapement.

In carrying out this invention in one form thereof, there is provided ahigh-speed drum printer which includes a cup-shaped drum having acylindrical wall of resilient material. On the external surface of thecylindrical wall of the drum there is arranged a series of typeformations. This series is disposed in a helical path on the peripheryof the cylindrical wall. Mechanism is provided for feeding the recordingmedium past the periphery of the cylindrical wall. Driving means isincluded for continuously rotating the drum about the axis of thehelical path and at the same time continuously translating the drumlongitudinally along the axis so that each type element passes aplurality of spaced printing positions on the medium, in continuoussuccession.

With this arrangement, a pivoted hammer is located with its strikingsurface inside of the drum. This hammer is supported on a carriage whichalso rotatably supports the drum so that the hammer may movelongitudinally with the drum when the drum is translating longitudinallyalong its axis. A hammer actuating mechanism is provided for selectivelyoperating the striking surface of the hammer against the inside surfaceof the cylindrical wall behind a selected type element when a selectedtype element passes one of the printing positions. The impact of theactuating surface of the hammer upon the inside surface of the resilientcylindrical wall, causes resilient flexing of the drum wall against themedium to selectively imprint characters thereon. Such a structureallows convenient front printing in conjunction with a drum printer byplacement of the hammer actuator inside the cavity of the drum. Theoverall drum printer is both compact and effective in operation.

BRIEF DESCRIPTION OF DRAWINGS The foregoing and other objects, featuresand advantages of this invention will be apparent from the followingdescription of the drawings inwhich:

FIG. 1 is a perspective view of a drum printer embodying one form of ourinvention;

FIG. 2 is a left end view of the printer of FIG. 1, with the motor, sideplate and selective driving mechanism removedto more clearly show thepaper feed mechanism, carrier, drum interior, and hammer structures;

FIG. 3 is a fragmentary rear view showing the hammer actuating mechanismand the mode of striking the flexible drum wall;

FIGS. 4 and 5 show fragments of the cylindrical wall and-type formationsthereon to illustrate by comparison the flexure of a formation inresponse to its actuation by the hammer;

FIG. 6 shows a modification of the drum and hammer arrangement for thedrum printer of FIG. l,which provides two hammers disposed inside of theresilient drum wall; and

FIG. 7 illustrates by means of a fragmentary perspective view, thehammer, its supporting structure, and the associated hammer actuatingmechanism.

DESCRIPTION OF THE PREFERRED EMBODIMENT OF THE INVENTION Referring nowto FIG. 1, there is shown a drum printer 11 for recording characters onpaper 13 carried by a feed roll 15. The general arrangement of the drumprinter 11 includes a slidable carriage 17 which supports a rotatableand slidable drum 19, together with a printing hammer 2]; a selectivedriving mechanism 23 for operating the drum l9 and hammer 21 in onedirection (i.e., to the right, viewing FIG. 1) across the paper 13; areturn mechanism 25 for bringing the drum and hammer back to theirstarting position on the left side of a page after each line has beenprinted; and a paper incrementing mechanism 27 for vertically spacingautomatically from one to the next line after each line of print hasbeen completed.

The selective driving mechanism 23 includes a motor 29 having its outputwheel 31 coupled to an emitter wheel 33 by means of driving belt 35. Theemitter wheel 33 includes peripheral teeth 37 which correspond inangular relationship to predetermined type characters or elements 39located on the flexible cylindrical wall 41 of drum 19. Moreparticularly, the emitter 43 preselects the desired tooth 37 of theemitter wheel 33 for each printing position of a line to determine whichprinting character 39 should be imprinted thereon.

The emitter wheel 33 is supported by means of a shaft 45 that has one ofits ends rotatably trunnioned in one side plate 47. The other end 49 ofthe shaft 45 is rotatably trunnioned in the other side plate 51.

Shaft 45 is threaded with an acme thread 53 having a pitch of threadsper inch. The threads 53 of the shaft 45 are also interrupted duringeach turn by a keyway slot 55 which runs longitudinally and axially fromone end to the other of the peripheral surface of the shaft. Directlyunderneath and parallel to the driving shaft 45, there is located afirst guiding shaft 57, which has one of its ends secured to side plate47 and the other end secured to side plate 51.

The slidable carriage 17 is structured so that it includes a generallyU-shaped body portion 59 having two upwardly extensive arms. 61 and 63connected to a bight portion 65. Arm 61 has a lower cylindrical bore 67for slidable bearing engagement with, the first guide shaft 57, and anupper cylindrical bore 69 for receiving thedrive shaft 45therethroughpThe other arm 63 includes a lower cylindrical bore 71 forproviding bearing cooperation with the first guiding shaft 57, and anupper cylindrical bore 73 for receiving the drive shaft 45 therethrough.

From viewing FIG. 1 it will be noted that an additional guide shaft 75is extended in parallel relationship to the first guiding shaft 57,between side plates 47 and 51. Shaft 75 receives a lateral bearing arm77 which extends frontwise (viewing FIG. 1) from the bight portion 65,to provide a partially cylindrical bearing channel 79 for stabilizingthe sliding movement of carriage 17.

From viewing FIG. 1, it will be further noted that there is secured tothe frontal face of upright 61 of body portion 59, a small electromagnet81. The electromagnet 81 includes coil 83 which surrounds one arm of aU-shaped core member 85, and a pivoted magnetizable arm 87 which isattracted by the magnet 81 upon energization of the coil 83. Attached tothe arm 87 is a small shaft 89 that is rotatably supported in a pair ofopposed apertures 91 located at the top of upright arm 61. The shaft 89has secured thereto a tongue 93 which is pivotally movable with bothshaft 89 as well as its attached magnetizable arm 87. Tongue 93 isnormally acted upon by a spring 95 so that its free end 97 is disposedupwardly and away from the threads 53 of shaft 45. The free end 97 oftongue 93 has integrally formed thereon a series of arcuate projections99. The projections 99 serve as a half nut in cooperation with thethread 53 of shaft 45. Thus, when the coil 83 of the electromagnet 81.is energized, magnetic arm 87 of the electromagnet is attracted towardthe coil so that tongue 93 pivots in opposition to its normal springbiasing force until projections 99 of the tongue are in threadedcooperation with the driving shaft 45. Then, upon rotation of the shaft45 about its bearings, carriage 1.7 is gradually driven in alongitudinal direction from left to right (viewing FIG. 1) by means ofthe threaded engagement of the tongue 93 with shaft 45.

On upright arm 63 of carriage body portion 59, there is disposed apivoted coupler 101 arranged for rotation on pivot pin 103, to lock thedrum 19 at the desired longitudinal position on carriage 17. Coupler 101has an arcuate surface 105 which engages an annular recess 107 formed inhub 109 of the drum 19. In addition, viewing FIG. 1, the drum 19includes the aforemen tioned flexible cylindrical wall 41. Wall 41 hasan annular internal groove which snaps into cooperation with anapertured metal disk 113 (FIG. 2). The disk 113 is preferably integralwith the hub 109. It is considered advantageous that the annular grooveof the drum .119

be located at the axial end of the drum located away from theelectromagnet 81., so that the drum 19 essen= tially provides acup-shaped recess for receiving hammer 21. Hub 113 has a key 114 (FIG.2) formed thereon for drivably coupling drum 19 to keyway slot 55 ofdrive shaft 45.

The type elements 39 are arranged in spiral fashion,

on the external periphery of the flexible cylindrical wall 41 with thesame pitch as the thread 53 ofshaft 45, in a manner well known in theart, so that upon each rotation of drum l9, withthe thread (projections99) of tongue 93 enmeshed with thread 53 of shaft 45, the

type elements 39 on cylindrical wall 41 all pass one" printing positionrelative to the paper 13.

Turning now to an importantaspect of the present invention which helpsachieve a low-cost, compact and efficient printing mechanism, it will benoted that on the side ofU-shaped body portion 59 opposite the lateralbearing arm 77 (viewing FIG. 1), there is located a hammer actuatingmechanism 115 (see FIG. 3). Ac-

tuating mechanism 115 involves a core member .117

having an upper arm 1 19 that extends through coil 121.

The core member 117 is secured to the U-shaped body portion 59 by meansof a non-magnetic plate 123 and screws 125. Plate 123 helps to support amagnetizable actuator 127 which is pivoted thereto by pin 129. The

operating finger 131 of actuator .127 engages the ing FIG. 7, the cornerarea 139 of hammer 21 has a 2 suitable aperture (not shown) to receive abearing pin 140 which extends through two opposite horizontallyextensivesides of the upright section .137 and is secured thereto.Hammer 21 is rotatable aboutits bear- I ing pin so that its actuatinghead 141 impacts on the inside surface of the cylindrical wall 41opposite the type 39 (FIG/1) to compress these element into engage.-ment with the printing medium (e.g., paper 13).

In FIGS. 4 and 5 there are shown two views to illustrate the manner inwhich the actuating head 141. of

hammer 21 engages the inside surface of cylindrical wall 41 of drum 19.Thus, FIG. 4 shows theactuating head 141 in its inactive position, inradial alignment with one of the printing characters 39. For thisposition, the head 141 is disposed radially inwardly and spaced apartfrom the aligned printing character 39.. FIG. 5 showsthe head 141 afterit has engaged theresilient wall behind the aligned printing character39. It

will be noted that the external or actuating face of the character 39,is thus thrust radially outwardly from the axis of rotation of the drum19 for engagement with the,

printing medium or a suitable carbonized ribbon adjacent to such amedium.

It will be seen that by securing the hammer actuating mechanism 115 tobody portion 59 of the slidable carriage 17, and locating the hammeractuating head .141

inside of the recess of the flexible drum 19, the hammer 1 21 translateslongitudinally with the drum. and is always in the proper printingposition. Such an arrangement is very compact and leads to significantadvantages in front printing. 1

The pivoted coupler 101 engages annular recess 107 of hub 109 of thedrum 19' to normally retain it into coupled engagement with the slidablecarriae 17. When it is desired to remove drum 19 for servicing, thearcuate portion 105 of the pivoted coupler is moved out of engagementwith the circular recess 107 to disengage the drum 19. The drum may thenbe slid longitudinally along shaft 45 for appropriate removal from theprinter 11, such as by first detaching side plate 51.

For returning the slidable carriage 17 to the left side of the pageafter the completion of each printed line,

a suitable return mechanism 25 has been provided. For the embodiment setforth in FIG. 1, the return mechanism 25 comprises a cord 143 which issecured to carriage body 59 by means of screw 144. Cord 143is extendedaround peripheral sections of the rotatable pully wheels 145 and 147.The end of the cord 143 opposite screw 144 is biased by spring 149,which is connected by link 150 to the side plate 51, so that thecarriage 17 is normally urged to its left or return position. Thus, whenthe slidable carriage 17 has reached the right side of the page or anyposition to the right of its normal starting position (on the left sideof the page), spring 149 exerts a pulling type biasing force on cord 143which causes the carriage to return'to its initial starting position, tothe left of the page.

Another important aspect of the present invention concerns the provisionof a novel and improved paper incrementing mechanism 27 in the drumprinter 11 (see FIG. 2). Essentially, the mechanism 27 includes anelongated actuator 151, a connecting rod 153 adjustably linked to theactuator 151 by a threaded nut 155, a rotatable rocker arm 157 coupledto the rod 153 at its bifurcated end 153a, a biasing spring 159 fornormally urging the rocker arm 157 in a clockwise direction of rotation(viewing FIG. 2), and a ratchet wheel 161 drivably associated with apawl 163, pivotally attached to the rocker arm 157 by pin 164.

The elongated actuator 151 has a ball-shaped end 165 which is acted uponby shoulder 167 located on the bottom of the slidable carriage 17. Thesupported end 169 of actuator 151 is bent over twice to provide a pairof arms 169a having aligned bearing apertures 17] (FIG. 1). The bearingapertures 171 receive a cylindrical pin 173 secured to a suitablesupport 174 so that the actuator 151 is rotatable about a vertical axiswith the ball-shaped end 165 movable in the same general direction asthe longitudinal axis of shaft 45.

Near the shorter end of the supporting section for actuator 151, thereis formed an extension 175 that is pivotally connected to the threadednut 155. Nut 155 is in adjustable engagement with a threaded end ofconnecting rod 153. The other end 153a of the connecting rod 153 ispivotally supported by means of a shaft 177 having its longitudinal axisin a horizontal direction. Shaft 177 also pivotally supports the ratchetwheel 161. The bottom end 179 of rocker arm 157 is connected to one endof the spring 159. The other end of the spring 159 is secured to thesupport 174. Spring 159 acts upon. the rocker arm 157 to bias it in aclockwise direction of rotation (viewing FIG. 2). The pawl 163 ispivotally linked to the other and opposite end of the rocker arm 157from the end 179. Pawl 163 is gravity operated so that whenever theratchet wheel rotates in a counterclockwise direction the driving end183 of pawl 163 first allows the ratchet wheel 161 to rotate and thenseats its sharp end in the next consecutive tooth. The shaft 177 iselongated and connected to a series of spaced apart driving spools (notshown) to drive the medium 13 and thereby progress flexible materialtherefrom one line space for each tooth of rotation of the ratchetwheel.

Another important advantage of the present invention resides in the factthat modular feed rolls may be provided with the printer 11. Forexample, in addition to handlingpaper material such as that shown infeed,

roll 15 for FIG. 1, the printing device 11 may also be interchangeablyused for print cards suitably fed toward the rear or drum 19. I

It will now therefore be seen that we have provided a new and improveddrum printer which readily lends itself to mass production manufacture.By placement of the hammer actuating surface inside of a flexible drumsurface, a compact and low-cost arrangement is achieved for frontprinting on either paper or cards. One of the significant advantagesresiding in such an approach isthat it is no longer necessary to actuatea print hammer through a variable thickness document (such as apassport). The particular type of printer embodying our invention may bereadily and beneficially used for a low-cost computer terminal.

Such a printer may also be utilized with two or more hammersadvantageously located inside of,the drum. An example of this particulartype of printer is shown in FIG. 6. Here, the structure of drum 19 andits flexible cylindrical wall 41 are essentially the same as for themain embodiment shown in FIG. 2. However, the slidable carriage 217 isdifferent, in that it is guided by first and second shafts 257 and 275which are in vertical alignment instead of horizontal alignment; Theshafts 257 and 275 are in slidable cooperation with apertures 267 and279, respectively, the latter of which resembles an open ended slot likeslot 79 of the FIG. 1 embodiment.

To enable the alternative embodiment of FIG. 6 to support two hammers 21that are diametrically opposed and located inside of drum 19, twoseparate and distinct hammer actuating mechanisms 215 are provided,which are suitably supported and carried by the carriage 217. For thisparticular modification of the original embodiment, each of the twodiametrically opposed hammers might be operable by separate and discreteactuating mechanisms so that one hammer might be printing on paper whilethe other is printing at the same time on ajournal or on tape, as shownby the dash lines of FIG. 6.

While in accordance with the Patent Statutes, we have described what atpresent are considered to be the preferred aspects of this invention, itwill be obvious to those skilled in the art that various changes ormodifications may be made therein without departing from the presentinvention.

What we claim is:

l. A high speed printer for recording characters on a medium comprising:

a rotatable drum having a cylindrical wall of resilient material,

a series of type formations disposed in a helical path on the peripheryof said cylindrical wall,

means for feeding the medium past the periphery of said cylindricalwall,

driving means for rotating said drum about the axis of said helical pathand at the same time translating said drum longitudinally along saidaxis so that each type formation will pass in substantially continuoussuccession past each of a plurality of spacedprinting positions on themedium,

a striking member located at least partially inside of said drum andmovable by said driving means together with said drum in a longitudinaldirection when said drum is translating longitudinally along said axis,and

means for selectively actuating said striking member against the insidesurface of said cylindrical wall behind a selected type formationwhenever a selected type formation passes one of said printingpositions, thereby causing resilient flection of said drum wall toselectively imprint characters on said medium;

said driving means comprising:

a motor,

an elongated drive shaft rotatably driven by said motor,

said shaft having a series of threads formed on its periphery and alongitudinal slot formed on the periphery of said shaft in parallelrelationship with the axis of rotation of said shaft,

therein for receiving said drive shaft,

pivoted and threaded element supported by said carriage and selectivelycooperable with the threads on the periphery of the drive shaft fortranslating said carriage along the longitudinal axis of the drive shaftwhen said shaft is rotatably driven by said motor and the pivotedelement is in threaded engagement with said drive shaft,

said drum including in addition to its cylindrical wall a hub, and

slidable carriage having at least one bore formed said hub having a keyformed thereon for cooperation with the longitudinal slot of said shaft,so that the drum is rotatably driven by the shaft upon rotation thereofby the motor. 2. The high speedprinter of claim 1 wherein said carriagefurther supports a pivoted latch for couplingsaiddrum to said carriage.

3. The high speed printer of claim 2 wherein the carriage furtherincludes two guiding channels, each of said guiding channels receiving arelatively fixed associ ated guiding shaft for guiding and stabilizingthe carriage during driven movement thereof in response to energizationof said motor.

4. The high speed printer of claim 3 wherein a spring biased cord isoperable between one side of said carriage and a fixed support to returnthe printing carriage to its starting position after a page has beenprinted 5. The high speed printer of claim 4 wherein theselectiveactuating mechanism for the striking member includes a pivoted armsupported by the carriage, said arm having a slot therein for supportingsaidstriking printing function, the other end of said striking memberbeing positioned on the carriage for selective actuation by amagnetizable member supported by said carriage.

1. A high speed printer for recording characters on a medium comprising:a rotatable drum having a cylindrical wall of resilient material, aseries of type formations disposed in a helical path on the periphery ofsaid cylindrical wall, means for feeding the medium past the peripheryof said cylindrical wall, driving means for rotating said drum about theaxis of said helical path and at the same time translating said drumlongitudinally along said axis so that each type formation will pass insubstantially continuous succession past each of a plurality of spacedprinting positions on the medium, a striking member located at leastpartially inside of said drum and movable by said driving means togetherwith said drum in a longitudinal direction when said drum is translatinglongitudinally along said axis, and means for selectively actuating saidstriking member against the inside surface of said cylindrical wallbehind a selected type formation whenever a selected type formationpasses one of said printing positions, thereby causing resilientflection of said drum wall to selectively imprint characters on saidmedium; said driving means comprising: a motor, an elongated drive shaftrotatably driven by said motor, said shaft having a series of threadsformed on its periphery and a longitudinal slot formed on the peripheryof said shaft in parallel relationship with the axis of rotation of saidshaft, a slidable carriage having at least one bore formed therein forreceiving said drive shaft, a pivoted and threaded element supported bysaid carriage and selectively cooperable with the threads on theperiphery of the drive shaft for translating said carriage along thelongitudinal axis of the drive shaft when said shaft is rotatably drivenby said motor and the pivoted element is in threaded engagement withsaid drive shaft, said drum including in addition to its cylindricalwall a hub, and said hub having a key formed thereon for cooperationwith the longitudinal slot of said shaft, so that the drum is rotatablydriven by the shaft upon rotation thereof by the motor.
 2. The highspeed printer of claim 1 wherein said carriage further supports apivoted latch for couplinG said drum to said carriage.
 3. The high speedprinter of claim 2 wherein the carriage further includes two guidingchannels, each of said guiding channels receiving a relatively fixedassociated guiding shaft for guiding and stabilizing the carriage duringdriven movement thereof in response to energization of said motor. 4.The high speed printer of claim 3 wherein a spring biased cord isoperable between one side of said carriage and a fixed support to returnthe printing carriage to its starting position after a page has beenprinted.
 5. The high speed printer of claim 4 wherein the selectiveactuating mechanism for the striking member includes a pivoted armsupported by the carriage, said arm having a slot therein for supportingsaid striking member, said striking member having an L shaped andrelatively flat configuration, one end of said striking member having asurface formed thereon for impinging upon the inside cylindrical wall ofthe drum thereby to perform a printing function, the other end of saidstriking member being positioned on the carriage for selective actuationby a magnetizable member supported by said carriage.